The tactics of terrorism are diverse. As important as the actual attacks is the cultivation in the target population of the fear of such attacks, so that the threat of violence becomes as effective as actual violence.

While advancements in technology, modernization, and globalization have helped many states prosper over the course of history, they have also opened terrorist groups to new tactics and weaponry. The different tactics that terrorist groups utilize can be very simple to extremely complex. In his book, Why Terrorism Works: Understanding the Threat, Responding to the Challenge, Harvard Law Professor Alan M. Dershowitz states that before the dawn of dynamite and automatic weapons, killings conducted by terrorists had to be done on a one-on-one basis.[1] Dershowitz also describes how the introduction of new weapons and technology has enabled terrorists to kill more efficiently and in greater amounts:

"The weapons of choice for earlier terrorists were the dagger, the noose, the sword, and the poison elixir. The introduction of the hand-thrown bomb and the pistol, and more recently the machine gun and plastic explosives, enabled terrorists to kill much more efficiently. Now weapons of mass, or ‘wholesale,’ destruction allow terrorists to ‘leverage’ their personnel, as proved by the events of September 11, 2001, in which a relatively small number of highly trained individuals armed with primitive box cutters and prepared to give up their own lives were able to use passenger jets as weapons of mass murder."[2]

Terrorist tactics tend to favor attacks that avoid effective countermeasures and exploit vulnerabilities.[3] As such, terrorist groups have the potential to utilize many different types of terrorism tactics depending on the circumstances and the perceived likelihood of success. Some tactics are more conventional and widely used in the operations of many terrorist groups. These tactics include shootings, hijackings, kidnappings, bombings, and suicide attacks. Other tactics are seen more unconventional and have only been used in a few instances, if at all. However, these unconventional tactics are perceived by government officials and experts alike as serious potential threats. Some types of unconventional terrorism tactics commonly recognized by terrorism experts are bioterrorism, agroterrorism, nuclear terrorism, and cyberterrorism.

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As a consequence of globalisation, the relative ease of access to the chemicals used to make explosives has made improvised explosive devices (IEDs) increasingly prominent. This has the dual effect of increasing the available firepower of terrorists who are generally far weaker than their targets as well as assuring the publicity necessary to attract sympathisers to their cause.

These may be implanted in automobiles to make a car bomb, planted on the roadside to detonate near target vehicles, or even strapped to the bodies of individuals for suicide attacks. From a tactical perspective, each of these methods have positives and drawback, for instance car bombs act as their own delivery mechanisms and can carry a relatively large amount of explosives with weights of up to and over 1000 pounds (450 kg),[4] while a suicide vest has a much smaller payload but may allow the wearer access to spaces and individuals that vehicles cannot.

Suicide terrorism is the most aggressive form of terrorism, pursuing coercion even at the expense of losing support among terrorists' own community. What distinguishes a suicide terrorist is that the attacker does not expect to survive a mission and often employs a method of attack that requires the attacker's death in order to succeed (such as planting a car bomb, wearing a suicide vest, or ramming an airplane into a building). In essence, a suicide terrorist kills others at the same time that he kills himself. Usually these tactics are used for a demonstrative purposes or to targeted assassinations. In most cases though, they target to kill a large number of people. Thus, while coercion is an element in all terrorism, coercion is the paramount objective of suicide terrorism.[5]

The number of attacks using suicide tactics has grown from an average of fewer than five per year during the 1980s to 180 per year between 2000 and 2005,[6] and from 81 suicide attacks in 2001 to 460 in 2005.[7] These attacks have been aimed at diverse military and civilian targets, including in Sri Lanka, in Israel since July 6, 1989,[8] in Iraq since the US-led invasion of that country in 2003, and in Pakistan and Afghanistan since 2005.

Between 1980 and 2000, the largest number of suicide attacks was carried out by separatist Liberation Tigers of Tamil Eelam of Sri Lanka. The number of attacks conducted by LTTE was almoust double that of nine other major extremist organizations.[9]

In Israel, Gaza and the West Bank, suicide bombings are an anti-Israel strategy perpetrated generally by Islamist and occasionally by secular Palestinian groups including the PFLP.[10]

The use of rocket and mortar attacks had been widely used from 1982–2012, in the example of the middle east rocket attacks against cities and settlements had been carried out by political entities such as Hizballa and Hamas (not counted as state terrorism) and to non political organization such as Islamic Jihad, Islamic Jihad Movement in Palestine, al-Qaeda and many others.

The number of attacks using explosive projectiles has grown after decrease in suicide attacks as can be seen in Palestinian rocket attacks on Israel,[11] according to the reports somewhere between 800000 people [12] to million and a half [13] are being in direct danger of mortar and missile range. In research published in 2011, 15,000 people had been treated or need treatment for PTSD[14] and 1,000 people are being treated in psychometric facilities due to reasons directly to mortar (qassam) and rocket attacks (Grad).[15][16][17]

Compared to suicide-bomb attacks, using vehicles as weapons is easier to plan and carry out without detection. The tactic does not require acquiring explosives. The weapon, a standard street-legal vehicle, is readily available in the target country and can be used without raising suspicion. According to a report by Stratfor global intelligence, using a vehicle as a terrorist tactic is nearly as effective, yet not as destructive as a suicide bombing.[18]

Bioterrorism is the deliberate release of viruses, bacteria, or other germs (agents) used to cause illness or death in people, animals, or plants.[19] Biological agents are typically found in nature, but it is possible that they can be changed to increase their ability to cause disease, make them resident to current medicines, or to increase their ability to be spread into the environment.[19] Biological agents in the hands of terrorists pose serious threats to states’ security because they can be easily spread through the air, through water, and through food.[19] Biological agents can also be difficult to detect and often do not cause illness for several hours to several days.[19] A prominent example of a bioterrorist attack on the United States is the September 2001 anthrax attacks. On September 18, 2001, several letters containing anthrax were sent to media outlets and the U.S. Congressional offices of Senator Thomas Daschle and Senator Patrick Leahy. Five Americans died from anthrax inhalation as a result of contact with the contaminated mail.[20] While the 2001 anthrax attacks were relatively small-scale, the United States government has taken several steps since to 2001 to pass legislation and initiatives aimed at better protecting the United States against biological attacks, improving the United States’ public health system, and improving the United States ability to respond to biological attacks.

A subset of bioterrorism, agroterrorism refers to the deliberate introduction of an animal or plant disease for the purposes of generating fear, causing economic losses, or undermining social stability.[22] The ultimate goal of agroterrorism in killing livestock and plants and contaminating food is to cause economic crises in the agricultural and food industries, social unrest, and loss of confidence in the government.[22] Many experts believe that the United States’ agricultural sector and food supply are among the most vulnerable and least protected of all potential targets of attack, and they believe that terrorists have taken note of this.[23] After American and allied forces overran some Al-Qaeda’s refuges in caves in eastern Afghanistan in 2002, they found U.S. agricultural documents and Al-Qaeda training manuals on targeting agriculture among thousands of other documents.[23]

Analysts have identified a number of characteristics of the United States’ agricultural system that make it very vulnerable to agroterrorism. Given that agriculture generally demands large expanses of land, farms are geographically dispersed in environments that are difficult to secure.[22] Also, livestock are usually concentrated in confined locations, which allows diseases to infect more animals quickly.[22] Although many experts believe the United States is susceptible to agroterrorism, they have never suffered from a large scale agroterrorism related attack. Many political scientists have identified the 1984 salmonella attack in The Dalles, Oregon as a small-scale example of an agroterrorism attack in the United States. A religious cult intentionally contaminated ten restaurant salad bars with salmonella in an attempt to influence a local election, sickening more than 750 people.[23] Even though the United States has not experienced a large-scale agroterrorism attack to date, similar to its anti-bioterrorism initiatives, the United States government has passed several pieces of legislation and started initiatives over the past few decades to better secure its agricultural system and prepare for potential attacks.

While no terrorist group has ever successfully acquired and used a nuclear weapon, many political scientists and prominent government officials consider nuclear terrorism to be one of the single greatest threats in global security. There is strong evidence that terrorist groups like Al-Qaeda are actively seeking to acquire nuclear weapons, and the plutonium or highly enriched uranium (HEU) needed to produce them.[30] Another serious concern is that weaknesses in many states’ nuclear security apparatuses have left them susceptible to theft or loss of HEU or plutonium. According to the International Atomic Energy Agency’s (IAEA) Illicit Trafficking Database (ITDB), there have been 18 incidents of theft or loss of HEU and plutonium reported in ITDB’s participating states.[30] Given these serious concerns, the United States, its allies, and international organizations like the United Nations have established several international agreements and initiatives to ensure that all states’ nuclear security standards are adequate and effective, and to secure all vulnerable and unprotected nuclear stockpiles around the world over the next few years.

In the developing age Information Technology, many political scientists and prominent government officials have become increasingly concerned about the ability of terrorist groups to execute cyber attacks and states’ vulnerabilities to these attacks. Cyberterrorism could potentially become an increasingly desirable tactic for terrorist groups given that they can be executed thousands of miles away from the target and are difficult to trace back to the perpetrator. In an October 2012 speech, United States Secretary of Defense Leon Panetta described the seriousness of a cyber attack on the United States: “A cyber attack perpetrated by nation states or violent extremists groups could be as destructive as the terrorist attack of 9/11. Such a destructive cyber terrorist attack could paralyze the nation.”[31] The term “cyberterrorism” was first coined by Barry Collin, a senior research fellow at the Institute for Security and Intelligence in California, in the 1980s.[32] The Center for Strategic and International Studies defines cyberterrorism as “the use of computer network tools to shut down critical national infrastructures (such as energy, transportation, government operations) or to coerce or intimidate a government or civilian population.”[33] Many experts believe that new vulnerabilities will be created as nations and their critical infrastructures become more dependent on computer networks for their operation.[33]

While concern is growing, cyberterrorism attacks still largely remain hypothetical, especially in the United States. In his report for the Center for Strategic and International Studies, James A Lewis writes that so far cyberterrorism has meant little more than propaganda and intelligence collection, and that no critical infrastructures have ever been shut down by cyber terrorist attacks.[33] Lewis also describes how terrorist groups like Al-Qaeda have made significant use of the Internet, but only as a tool for intra-group relations, fundraising, and public relations.[33] An Al-Qaeda training manual entitled “Military Studies in the Jihad Against the Tyrants” explicates that explosives are the preferred weapon of terrorists because “explosives strike the enemy with sheer terror and fright.”[33] While explosions are dramatic, strike fear into the hearts of opponents, and do lasting damage, cyber attacks, like some other types of terrorism tactics, simply do not have the same dramatic and political effect that terrorists seek. Some political scientists, like Lewis, argue that terrorist organizations like Al-Qaeda might use cyber attacks to disrupt emergency services in order to reinforce and multiply the effect of a physical attack.[33]

In 2004, the European Council recognized the "need to ensure terrorist organisations and groups are starved of the components of their trade," including “the need to ensure greater security of firearms, explosives, bomb-making equipment and technologies that contribute to the perpetration of terrorist outrages."[35]

Terrorist groups may arrange for secondary devices to detonate at a slightly later time in order to kill emergency-response personnel attempting to attend to the dead and wounded. Repeated or suspected use of secondary devices can also delay emergency response out of concern that such devices may exist. Examples include a (failed) device that was meant to release cyanide-gas during the February 26, 1993 World Trade Center bombing; and a second car bomb that detonated 20 minutes after the December 1, 2001 Ben Yehuda Street Bombing by Hamas in Jerusalem.

There are and have been training camps for terrorists. The range of training depends greatly on the level of support the terrorist organization receives from various organizations and states. In nearly every case the training incorporates the philosophy and agenda of the groups leadership as justification for the training as well as the potential acts of terrorism which may be committed. State sanctioned training is by far the most extensive and thorough, often employing professional soldiers and covert operatives of the supporting state.

Where terrorism occurs in the context of open warfare or insurgency, its perpetrators may shelter behind a section of the local population. Examples include the intifada on Israeli-occupied territory, and insurgency in Iraq. This population, which may be ethnically distinct from the counter-terrorist forces, is either sympathetic to their cause, indifferent, or acts under duress.

Terrorist financing generated through the use of underground smuggling tunnels and the probability that a specific smuggling tunnel or terrorist criminal social network will use the smuggling tunnel to launch a kidnapping operation or terrorist attack has been addressed in the literature.[37][38]

Even though older communication methods like radio are still used, the revolution in communication technology over the past 10–15 years has dramatically changed how terrorist organizations communicate. E-mails, fax transmissions, websites, cell phones, and satellite telephones have made it possible for organizations to contemplate a global strategy. However, too great a reliance on this new technology leaves organizations vulnerable to sophisticated monitoring of communication and triangulation of its source. When Osama bin Laden found out that his satellite phone conversations were being intercepted, he ceased using this method to communicate.[39]

The primary weapon of terrorism is fear, destruction and killing are not an end in and of itself, but a tool to create fear and terror in the minds of the enemy. In an asymmetric situation an enemy who cannot be defeated militarily may be defeated psychologically, that they may come to fear attack and its consequences so much they may become willing to forgo a superior military position in order to be free of the cause of that fear.

If a terrorist group can carry out enough credible attacks then "coded warnings" or planted electronic chatter, designed to be intercepted, can cause as much disruption as a genuine attack or bomb. As long as the supposed attacks are plausible and they are supported by the occasional genuine attack, the authorities will be forced to expend resources to combat non-existent devices, dummy bombs and plain fictions, disrupting the lives of citizens, and feeding the public's fear.